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UNITED STATES DEPARTMENT OF AGRICULTURE 

^ BULLETIN No. 939 

Contribution from the Bureau of Animal Industry 
JOHN R. MOHLER, Chief 








Washington, D. C. 



April 23, 1921 



THE TURKEY AN IMPORTANT FACTOR IN THE 
SPREAD OF GAPEWORMS/ 

By B. H. Ransom, Chwf, Zoological Division. 



CONTENTS. 

Page. 



Examination of market chicliens 

and turkeys 

Experimental work 

Factors in ttie spread of gape- 
worms 

Investigations on Maryland 
farms 



Significance of turkeys in relation 

to gapes formerly unrecognized — 

Turkey the preferred host of the 

gapeworm 

How to avoid losses in chickens 

Conclusions 

List of references 



Page. 

10 

10 
11 
12 
13 



EXAMINATION OF MARKET CHICKENS AND TURKEYS. 



■pOR THE PURPOSE of collecting some statistics on the preva- 
lence of gapeworms {Syiigamus trachealis) in the vicinity of 
Washington, D. C, and of obtaining material for use in experiments, 
examinations were made of the tracheas of 635 chickens killed for 
sale at poultry stalls in Center Market during the latter half of 
December, 1916, and the months of January and February, 1917. 
Nothing definite is known as to the ages of these chickens except 
that the chickens were all obviously large enough for food purposes. 
Probably none were less than six months old, most of them likely 
were older, and no doubt many were a year old or more. No gape- 
worms were found. 

At the same time the tracheas of turkeys from the same market 
were similarly examined. The ages of the turkeys, as in the case of 
the chickens, were uncertain, but undoubtedly all the turkeys were 
at least 6 months old, and many of them were probably more than a 
year old. During the period mentioned the tracheas from 386 tur- 
keys were examined. The next year, beginning March 2, 1918, an- 

1 The writer is greatly indebted to Dr. Lawrence Avery, of the Bureau of Animal In- 
dustry, for assistance rendered in carrying out the investigations reported in this paper. 
22888° — 21 — Bull. 9.30 1 

ilAWJiw^iJipft 



2 BULLETIN 939, U. S. DEPARTMENT OF AGRICULTURE. 

other series of 115 was examined, and during the month of Novem- 
ber, 1918, a final series of 178 ; in all, 679 turkey tracheas were ex- 
amined. In the case of the chickens practically the entire trachea 
was obtained from each bird, but in the case of the turkeys usually 
only a portion of the trachea was secured, so that as a rule an exami- 
nation of the entire trachea could not be made. 

In the first series of turkey tracheas (386 examined in December, 
1916, and January and February, 1917) gapeworms were found in 
89, and characteristic lesions marking the former location of gape- 
worms in 3 others, a total of 92, or 23.8 per cent. In the second series 
(115 examined in March, 1918) worms were found in 17 and a gape- 
worm lesion in 1 other, a total of 18, or 15.7 per cent. In the third 
series (178 examined in November, 1918) worms were found in 43, 
or 24.2 per cent. The percentage of turkey tracheas infested out of 
the total number examined was 22.5 per cent. It is possible that the 
lower percentage observed among the tracheas examined in March as 
compared with those examined in December, January, and February, 
and in November following, was the result of having more incomplete 
specimens of tracheas than were generally secured in the two latter 
series. In an}^ event, in view of the fact that throughout the three 
series incomplete tracheas were the rule, it appears quite certain that 
more cases of infestation would have been found if the entire trachea 
could always have been secured. It is, therefore, fair to conclude that 
the percentage of infestation among the turkeys examined was in 
reality higher than the 22.5 per cent actually found. Counting the 
gapeworm lesions found without worms attached as representing 
worms, and counting the paired male and female as a single worm, a 
single worm was present in 91 cases, 2 worms in 36 cases, 3 worms in 
14 cases, 4 worms in 6 cases, 5 worms in 3 cases, 7, 9, and 18 worms 
in 1 case each. 

In view of the complete absence of gapeworms from a large series 
of adult and approximately adult chickens, and their common occur- 
rence in a similar series of adult and approximately adult turkeys, 
all obtained at the same market and at the same season of the year, 
it would appear that adult chickens are poorly adapted as hosts 
for gapeworms. Evidently the occurrence of gapeworms in adult 
chickens in the general locality of Washington, D. C, must be ex- 
ceedingly rare, though, as is well known, gapeworms are of frequent 
occurrence in yoimg chicks in this as well as in many other localities. 
On the other hand, it is evident that not merely young turkeys may 
harbor gapeworms, but that in the locality mentioned these parasites 
are very common in adult turkeys. Although, as noted, the ages of 
the various turkeys from the Washington market were uncertain, 
many of the turkeys examined were no doubt considerably more than 



UBR.ARY-OF eONGRl:SS 

MAY 6*1921 

0.0C U ivi E iMTo : / i V « ^' ON 



1?3 



THE TURKEY IMPORTANT IN THE SPREAD OF GAPEWORMS. 3 

a year old. That turkeys above 3 years of age may harbor gape- 
worms is established by the fact that a turkey which was kept at the 
Bureau of Animal Industry Experiment Station, Bethesda, Md., for 
three years after it was brought there was found after its death to 
be infested with a pair of gapeworms. 

EXPERIMENTAL WORK. 

Experiments in artificially infecting chickens of various ages with 
gapeworms were carried out as follows : To provide material for 
infecting the chickens, cultures were made at first from gapeworms 
collected from the tracheas of turkeys. Later manj^ of the worms 
collected from the artificially infected chickens were also used in mak- 
ing cultures. The worms were chopped into small pieces and the 
eggs released by tearing apart the fi-agnients of the uteri in a small 
quantity of water. The water containing particles of worms and the 
eggs was spread on the surface of a sterilized medium culture made 
from chicken feces mixed with powdered animal charcoal. This was 
kept moist in a petri dish and allowed to incubate at room tempera- 
ture. After about two weeks' incubation a large proportion of the 
eggs contained fully developed larvse, manj^ of which common!}' 
hatched and continued active for long periods after hatching. The 
cultures were then ready for use and were fed to the chickens by plac- 
ing small portions scraped from the surface of the culture nredium 
directly into the mouth and making sure that the birds swallowed the 
material. The chickens used in the experiments, except the adults, 
were hatched in incubators and kept from exposure to gapeworm 
infection until used. Usually only one feeding was given, and in 
most cases the chicken, if it did not die earlier, was killed two weeks 
after feeding the infectious material. Occasionally chickens were 
killed for examination in less than two weeks after infection. The 
tracheas and lungs were examined for gapeworms, the latter by dis- 
section in physiological salt solution, a lens being used for the dis- 
covery of small, incompletely developed worms. Altogether 139 
chickens of different ages were thus fed infectious gapeworm 
material. The results are shown below. 

Results of artificially infecting chickens with gapeworm material. 



Ase of chickens when fed. 


Number 
fed. 


Number 
infected. 


Per cent 
infected. 




47 
32 
32 
28 


41 

27 
21 

8 


87 




84 


9 to 20 weeks 


66 




29 







4 BULLETIN 939, U. S. DEPARTMENT OF AGRICULTURE. 

From the data shown in the table it seems evident that as chickens 
grow older they tend to become less susceptible to infection with gape- 
worms. Apparently, therefore, the most likely reason no gapeworms 
were foLmd among the 635 chickens from the Washington market was 
that these chickens when examined had reached an age at which they 
were no longer favorable hosts for gapeworms. Probably some of 
them had been infested earlier in life but had afterwards lost their 
parasites. How long gapeworms will persist in youhg chickens that 
do not succumb to the infestation is uncertain. That adult chickens, 
however, in those unusual cases in which they become infested with 
gapeworms, are likely to harbor the parasites only temporarily is 
indicated by some of the findings in the following experiments : 

Twelve adult chickens a year old or more were fed gapeworm 
material from cultures on April 26, 28, 30, May 2, 4, 7, 9, and 11, 
altogether receiving 8 feedings, except one which was killed May 7, 
before feeding time, and hence received only 5 feedings. Material 
from the same cultures was fed to 12 1-week-old chicks April 24, 
28, 30, May 2, and 4. All the young chickens died of gapes in 11 
to 27 days after the first feeding, and all were found infested with 
gapeworms. Except the one killed May 7, 11 days after the first feed- 
ing, the adult chickens were killed 16 to 29 days after the first 
feeding and 1 to 14 days after the last feeding. Gapeworms 
were found in only 3 out of the 12. The lungs of one killed 16 days 
after the first feeding and 1 day after the last feeding contained an 
unpaired female 2.5 mm. long, and in the trachea were two pairs, 
the females being 6.5 mm. and 10 mm. long, respectively. The 10 
mm. female was producing eggs. Another chicken that was killed 
18 days after the first feeding and 3 days after the last feeding har- 
bored in the trachea a single pair of worms. The female of this pair 
measured 13 mm. in length and was depositing eggs. In the trachea 
of the third chicken, killed 29 days after the first feeding and 14 days 
after the last feeding, there were 7 dead males without females, 4 
living males without females, 3 living females with dead males, 1 
liAdng female with a living male, and 1 living female without a male. 
The last two females contained apparently viable eggs, but in the 
other three females the eggs were apparently nonfertile, dark, and 
unnatural in appearance. All the worms, alive and dead, were firmly 
attached to the trachea. The living worms were enveloped in a thick 
layer of mucus. 

On another occasion 6 adult chickens probably a little less than a 
year old were fed with a gapeworm culture. Seven days later one 
was killed. No worms were found. A second chicken, killed 8 days 
after feeding, had one unpaired worm, one pair of coupled worms in 
the lungs, and 14 pairs of coupled worms in the trachea, all imma- 



THE TURKEY IMPORTANT IX THE SPREAD OF GAPEWORMS. 5 

ture, those in the trachea evenly distributed from bronchi to larynx. 
The females in the trachea measured 3 to 6 mm. in length. The 
worms in the trachea were enveloped in masses of very viscid, tena- 
cious mucus and none apparently were attached to the wall of the 
trachea. Another chicken was killed 11 days after feeding and was 
found to be free from parasites. Twenty-eight days after feeding, 
microscopic examination failed to show gapeworm eggs in the feces 
of the three surviving chickens. The folloAving day one of them was 
killed and found to be free from parasites. Thirty-one days after 
the first feeding the two surviving chickens were fed with a gape- 
worm culture. Eight da^'^s after this feeding the chickens were 
killed. One of them was free from parasites, the other had one 
young worm in the lungs, and a pair of coupled worms in the 
trachea. The female of this pair was ruptured in removal but 
measured 15 mm. or more in length and contained eggs ready for 
oviposition. This pair of worms was enveloped in a mass of tena- 
cious mucus. Evidently the worms in the trachea came from the first 
feeding of gapeworm material, 39 davs before the chicken was 
killed. 

The findings in the case of one of the chickens referred to sug- 
gest very strongly that the worms that had succeeded in establisliing 
themselves in the trachea were having difficulty in maintaining them- 
selves, as 10 of the 15 males present 29 days after infection were 
dead though firmly attached to the trachea, and as the living worms, 
both males and females, were enveloped in a thick layer of mucus, 
indicat-ve perhaps of a strong reaction, on the part of the host, that 
would soon destroy them. In two of the other chickens also the 
unusually large masses of mucus enveloping the worms suggest the 
likelihood of the early death or expulsion of the parasites. In any 
event it is evident, since in the one instance a large proportion 
of the gapeworms present 29 days after infection had died after 
reaching maturity, that gapeworms in adult chickens, when they 
succeed in establishing themselves in the trachea, sometimes die 
within a month after infection, infestation with gapeworms in 
such cases thus being of brief duration. Further evidence of the 
transient nature of gapeworm infestation in adult chickens is 
given by Waite (1920, p. 115), who fed about 150 earthworms 
from gapeworm-infested chicken runs to three yearling hens. Fif- 
teen days later gapeworms could be distinctly seen in the tracheas 
of two of them by looking down their throats in a good light. Two 
weeks later the worms had disappeared, and when the hens were 
killed and examined 72 days after the feeding with the earthworms, 
no signs of gapeworms were found. 

In view of the difficulty of infecting adult chickens with gape- 
worms, the likelihood of the brief duration of infestation in cases in 



6 BULLETIN 939, U. S. DEPARTMENT OF AGRICULTURE. 

which the worms succeed in developing to maturity in adult chickens 
and the failure to find any gapeworms among a large number of 
adult chickens obtained from a certain market, though the parasites 
were of common occurrence in adult turkeys from the same market, 
it seems evident that adult chickens are not likely to be of great im- 
portance as carriers of gapeworms. On the other hand it is certain 
that sometimes they may harbor gapeworms for brief periods at least. 

Besides the fact that adult chickens occasionally may be infected ex- 
perimentally may be cited the following instance of infestation follow- 
ing exposure to infested ground. A chicken at least 22 months old and 
probably considerably more than 2 years old died at the Bureau of 
Animal Industry Experiment Station with a history indicating that 
it had been kept at least a year in a pen that had previously been 
used in gapeworm experiments. This hen was in poor condition, 
greatly emaciated, and devoid of the usual subcutaneous and visceral 
fat. Besides nematodes and tapeworms in the intestine there were 
found in the trachea a female gapeworm 21 mm. long with a male 
5 mm. long, and another female about 10 mm. long, with a male 
4.6 mm. long. The smaller female contained eggs, but well-developed 
eggs were not found in the larger female. 

This case perhaps should be taken as an indication of the possibility 
that as chickens become old and debilitated their susceptibility to 
gapeworms tends to increase again after having diminished as they 
approached maturity. Such an explanation would be in harmony 
with the frequently observed fact that certain parasites are more 
common in young and very old animals than in those of middle age. 
No definite conclusion, however, is possible from a single case. 

In marked contrast to adult or nearly adult chickens, adult turkeys 
can easily be infected experimentally with gapeworms, as would be 
expected from the fact that the wonns have been found to be 
naturally common among adult turkeys. The following experiment 
shows the results of attempts to infect chickens approaching ma- 
turity, young chickens, and adult turkeys, respectively, using in- 
fective material from the same source. 

Three chickens 21 weeks old at the beginning of the experiment 
were fed portions of gapeworm cultures November 29, December 18, 
20, 27, January 3, 31, February 28, and March 31. Beginning Febru- 
ary 28 the chickens were kept on ground that was contaminated with 
gapeworms. The feces of these three chickens were examined Janu- 
ary 3, 13, 17, 25, 31, February 8, 15, 22, 28, and March 28, and the 
feces of two of them also on April 22, always with negative results. 
One of the chickens was killed on April 8 and was free from gape- 
worms, as were also the other two, killed on May 24. 

Some of the culture fed on January 31 was fed on February 7 to 
three chicks 8 weeks old, and these chicks when killed 14 days later 



THE TURKEY IMPORTANT IN THE SPREAD OF GAPEWORMS. 7 

harbored, respectiveh', 9'2, 75, and 36 pairs of «:apeworms in their 
tracheas, the females ranging in size from 4 to 11 mm. Besides the 
Tvorms in the trachea there were a few immature gapeworms in the 
lungs of each chicken. 

Some of the same culture was fed on February 7 to three turkeys 
nearly a year old. Xineteen days later one of the turkej^s was 
observed to be sick and was killed. There were no gapeworms found 
in the lungs, but 483 pairs were present in the trachea, the females 
averaging 24 mm. in length. The feces of the two remaining turkej^s 
were first examined 21 da3's after infection and at this time con- 
tained large numbers of gapeworm eggs. The birds were coughing 
and there was a brown crust on their bills, formed by the drying of 
expectorated mucus. On March 17, 3S days after infection, these 
two. turkeys were still coughing, but the brown crust was no longer 
present on their bills. On April 14, G6 days after infection, gape- 
worm eggs were still present in the feces. April 29, one of the 
turkeys which had been ailing was killed, the lungs and one bronchus 
being found affected with a gangrenous necrosis. The trachea 
contained 22 pairs of gapeworms, the females averaging 33 mm. in 
length; also many broken pieces of dead Avorms were found. The 
third turkey was kept alive. December 16, 10 months after infection, 
an examination of the feces of this turkey failed to show gapeworm 
eggs. 

In this experiment adult turkeys (nearly a year old) and young 
chickens (8 weeks old) became heavily infested as the result of a 
single feeding with gapeworm material, while chickens approaching 
maturity (21 weeks old) that were fed repeatedly with gapeworm 
material (including material from the same culture as that fed to 
the turkeys and the 3'Oung chickens) failed to become infested. Evi- 
dently, therefore, adult turkeys and young chickens are much alike 
in their susceptibility to gapeworm infection, and in this respect both 
are quite different from adult chickens or chickens approaching 
maturity. 

FACTORS IN THE SPREAD OF GAPEWORMS. 

From the results of the investigations briefly recorded above, it 
would seem that turkeys are an important factor in the spread of the 
gapcAvorm, and that adult chickens are relatively unimportant as 
carriers of the parasite. In the perpetuation of gapeworms from year 
to year on infested poultry farms the two cliief factors appear to be 
turkeys and contaminated soil. Whether guinea fowls are like turkeys 
in commonly harboring gapeworms throughout life or whether they 
are like chickens and tend to lose their susceptibility as they become 
mature is uncertain. Little is known also as to the relation of pea- 
fowls, ducks, geese, pigeons, and various wild birds to the spread of 



8 BULLETIN 939, V. S. DEPAKTMENT OF AGRICULTURE. 

gapeworms. There is little question, however, that the turkey is more 
important than any other bird as a reservoir of infection, and it 
is essential, if losses from gapes are to be avoided, that the part 
played by the turkey in spreading and perpetuating gapeworms 
should be borne in mind by the poultry raiser. The relation of the 
turke}^ to gapes in chickens is commonly overlooked, largely, no 
doubt, because young turkeys are usually less seriously affected 
by gapeworms than young chickens, and because old turkeys har- 
boring the parasites rarely show any visible evidence of infestation, 
so that they are not likely to be suspected as a source of the disease 
that plays havoc among the young chickens. 

Whether, in the absence of turkeys from a farm, gapeworm dis- 
ease among chickens will regularly disappear has not been definitely 
established, but it seems probable that it may often do so. Though 
it is certain that contaminated soil will remain infectious for a long 
time and that infection in the soil may persist from one year to the 
next, nevertheless it may be that, as a rule, chickens alone will not 
perpetuate the infection. A large proportion of the young chickens 
that become infested die of gapes before there has been much oppor- 
tunity for scattering the eggs of the gapeworms, and since chickens 
as they grow older tend to become not only less susceptible to infec- 
tion but also more and more unfavorable as hosts of the gapeworms 
acquired at an earlier age, the infested chickens that do not die of 
gapes probably do not continue long to harbor the worms and so are 
unlikely to spread much infection. In view of these apparent limita- 
tions to the reinfection of the soil by chickens it seems not unlikely 
that gapes will be found to have a tendency to disappear from places 
where no turkeys are kept. 

INVESTIGATIONS ON MARYLAND FARMS. 

Evidence gathered from inquiries by Dr. Lawrence Avery and 
the writer among poultry raisers in several localities in Mary- 
land is insufficient to show that gapes will usually die out on farms 
where there are no possible hosts other than chickens, but it is cor- 
roborative of the statements that have been made as to the great im- 
portance of the turkey as a source of infection. In fact, it was found 
that in the absence of turkeys either no gapes occurred among the 
chickens or the trouble from this cause was practically always slight. 
On the other hand, where turkeys were present considerable losses 
among the chickens as a result of gapes were almost always reported. 
Inquiries were made on 41 farms. On 16 farms where there was 
no history of the association of turkeys with the chickens, gapes 
was reported in eight instances, no gapes in the other eight. On 
one farm where there M-ere said to be numerous cases of gapes 
among a flock of 500 chickens, turkeys were kept the preceding 



THE TURKEY IMPORTANT IN THE SPREAD OF GAPEWORMS. 9 

5'ear, but it was said that they never came near the chicken yards. 
A dozen guinea fowls were kept on this farm and mingled with 
the chickens. On two other farms where there was said to be 
considerable trouble with gapes, guinea fowls were kept in one case, 
but there were neither guinea fowls nor turkeys in the other. On the 
other 5 farms where gapes was reported in the absence of turkeys, 
few cases were said to have occurred. On 25 farms where there was 
evidence of the contamination of the chicken runs by turkeys, gapes 
was reported in all but one case. Here there were about 300 chickens 
and 70 turkeys roaming at will over the farm. The turkeys and 
chickens, however, were housed on different plots of ground, neither 
of which had been used for poultry during several years preceding. 
On two farms there were said to have been no cases of gapes until 
after turkeys were brought to the place. In another instance a man 
who for five years had been on a farm where turkeys were kept by the 
former occupant, had gapes among his chickens for a year or two after 
coming to the farm, but had had none since. On two farms where 
only a few cases of gapes occurred among the chickens, it was stated 
that the turkeys were kept in the fields, and never or rarely were 
brought into association with the chickens. On another farm where 
there were a few cases of gapes no turkeys were kept, but turkeys 
from the neighboring farm frequented the place. In a number of 
other instances no turkeys were kept, but turkeys from neighboring 
farms were accustomed to mingle with the chickens. 

Two neighboring farms that were visited during the season of 
the year when gapes is prevalent among young chickens afforded a 
striking contrast. On one farm where turkeys were kept entirely 
away from the chickens and never mingled with them nor came to 
the place where the chickens were kept there had been no gapes 
among the chickens. On the other farm several broods of young 
chickens were confined in small pens on the lawn in front of the 
farmhouse. Turkeys of various ages were feeding on the same 
lawn. Many of the young chickens were showing the characteristic 
symptoms of gapes. 

Though the data that have been collected concerning gapes on 
farms are necessarily more or less inaccurate because of the uncer- 
tainty as to the reliability of the information given by the persons 
of whom inquiries were made, the evidence obtained from this 
source nevertheless indicates that in the localities in which the ques- 
tion has been investigated gapes is more common and more serious 
on farms where turkeys and chickens are kept together than on farms 
where only chickens are kept, that the disease has a tendency to die 
out in the absence of turkeys, and that it commonly does not appear 
on a farm until after the introduction of turkevs. 



10 BULLETIN 939, U. S. DEPAKTMENT OF AGRICULTURE. 

SIGNIFICANCE OF TURKEYS IN RELATION TO GAPES FORMERLY 

UNRECOGNIZED. 

From the literature on gapes one may gather further evidence of 
the importance of the turkey as a carrier of gapeworms, though the 
peculiar significance of the turkey in relation to gapes has not been 
recognized by former writers. In the first published record of gapes 
Wiesenthal (1799) called attention to the frequent occurrence of the 
disease in Maryland and stated that it was most prevalent among 
young turkeys and chickens bred upon old-established farms. The 
first published record of gapes in England is that of Montagu 
(1811), who notes that it generally attacks chickens at the age of a 
month to 6 weeks, and that it "seems to be peculiar to the young 
of the common domestic fowl, since neither my turkeys nor ducks, 
all of which are reared together upon the same spot, have even l^een 
attacked." 

Von Pocci (1904), in discussing an outbreak of gapes among 
young pheasants in Bavaria, which killed about 60 per cent of the 
birds, incidentally remarks that turkeys were used as brood hens 
for young pheasants. The first record of gapes in Norway (Home, 
1910) is based upon the discovery of gapeworms in two 3'oung 
turkey poults and two young chickens from the same poultry farm. 
How frequently turkeys have been associated with the occurrence 
of gapeworms among chickens, pheasants, and other birds in Europe 
is not indicated in the published reports that have come to the 
writer's attention other than those just mentioned. These, however, 
are very suggestive and, together with the observations recorded in 
the present paper, may be taken as an indication of the probability 
that the turkey has been chiefly, if not entirely, responsible for the 
spread of the gapeworm to various parts of the world. 

TURKEY THE PREFERRED HOST OF THE GAPEWORM. 

It would seem quite probable that the gapeworm, like the turkey, 
was originally limited to America and that it has reached other 
countries only as it has been carried by the turkey, which, because 
of the tolerance it has to infestation with the gapeworm, may be 
looked upon as the natural host of this parasite. 

The fact that the gapeworm in turkeys grows to a larger size than 
it does in chickens may be taken as evidence, in addition to that 
already given, that the turkey as compared with the chicken is the 
preferred host of the parasite. The difference in the size of the 
worms may be a simple correlation with the size of the trachea, but 
it seems more likely that other conditions than the mere size of the 
trachea play a part in bringing about the differences in the size of 
gapeworms in chickens and turkeys. The maximum length of gape- 



THE TURKEY IMPORTANT IN THE SPREAD OF GAPEWORMS. H 

worms observed by the writer in chickens 14 clays after infection 
has been 17 mm. Usually the length attained in this period is less, 
commonly being 12 to 14 mm. The longest gapeworm observed by 
the writer in chickens measured 21 mm. in length. This was found 
in an old. debilitated chicken, mentioned on page 6, which had been 
infested for an unknown period. Some of the gapeworms present in 
an adult turkey 19 days after infection measured nearly 30 mm. in 
length, and worms measuring 24 mm. were common. In natural cases 
of infestation gapeworms in turkeys have been found commonly to 
measure 30 to 40 mm. in length, and have been found as long as 
50 mm. The measurements given are those of mature females that 
had begun oviposition or that contained eggs ready to be deposited. 

HOW TO AVOID LOSSES IN CHICKENS. 

From what has been determined as to the frequent occurrence of 
gapeworms in turkeys, the susceptibility of old as well as young 
turkeys to gapeworm infection, the diminishing susceptibility of 
chickens to infection as the}' groAv older, and the rarity of gape- 
worms among adult chickens, it would seem that the chief element in 
the spread and maintenance of gapeworm infection, leaving infested 
soil out of consideration, is the turkey. The eggs of the gapeworm 
are scattered over the soil in the feces of infested turkej^s. Later 
some of these eggs or the larvae that have hatched from them are 
picked up again by the turkeys and more egg-producing worms de- 
velop in them to add to the number of those already present. Thus 
the stock of young worms in the soil and adult worms in the turkeys 
is maintained. Meanwhile young chickens may also pick up gape- 
worm eggs or larval worms from the ground where the eggs have 
been distributed by the turkeys, with the result that they soon show 
symptoms of gapes. As chickens young enough to be readiW sus- 
ceptible to infection with gapeworms usually die from gapes soon 
after they begin to show symptoms of the disease they are not 
likely to add much to the infection already in the soil. Older 
chickens likewise do not scatter much infection because the eggs and 
larval worms that they pick up either do not develop on account of 
the diminished susceptibility of the chickens or, if the worms do 
succeed in developing to egg-producing maturity, they are unlikely 
to survive for more than brief periods. Chickens, therefore, may be 
considered to play a small part, compared with turkeys, in infecting 
the soil with gapeworms, and to be of minor importance as reservoirs 
of infection. By keeping turkeys away from young chickens and 
providing the latter with runs where there have been no turkeys 
within a year or two and where, if used previously by young chickens, 
there have been no cases of gapes in recent years, the danger of losses 



12 BULLETIN 93&, U. S. DEPARTMENT OF AGRICULTURE, 

from gapeworm can be greatly reduced, inasmuch as infection of the 
runs by the brood hens is not often likely to occur because of the 
rarity of gape worms among adult chickens. As the eggs and larvae 
of gapeworms have been kept alive in the laboratory for more than 
eight months at a temperature ranging from 70° to 95° F., and for 
more than a year at a temperature of about 50° F. (writer's observa- 
tions), it is advisable not to allow young chickens to run on once- 
contaminated ground until after a considerable period of time has 
elapsed, not less than a year at least, since its exposure to contamina- 
tion. Consequently it is important in locating new runs for young- 
chickens on farms where gapes has been jDrevalent to select a spot that 
is known to have been but little, if at all, frequented by turkeys within 
at least a year. Naturally also it would be unwise to select a spot 
where chickens with gapes had been the year before, even if in the 
meantime there had been no chance of contamination by turkeys. As 
a rule, in order easily to secure immunity from gapeworm losses 
among chickens, it may be found necessary to abandon the keeping of 
turkeys on farms where chickens are raised, because of the difficult}^ 
of controlling the turkeys so as to prevent contamination of the 
chicken runs. In fact the simplest way of preventing gapes among 
chickens seems to be to exclude turkej-s from farms where chickens 
are raised. 

CONCLUSIONS. 

The turkey is probably the natural host of the gapeworm. 

Adult turkeys as well as young turkeys commonly harbor gape- 
worms though they may show no symptoms of infestation. 

The turkey is apparently the chief agent in the spread of gape- 
worms to new localities and is apparently the principal source of 
infection to the soil on poultry farms where gapes is prevalent. 

Gapes among chickens appears to be more prevalent on farms 
where turkeys frequent the chicken runs than on farms where there 
are no turkeys. 

Available evidence indicates that gapes has a tendency to dis- 
appear from farms following the removal of turkeys. 

Chickens, unlike turkeys, are readily susceptible to infection with 
gapeworms only while they are young. They become less susceptible 
to infection as they grow older. 

Adult chickens, at least in some localities, rarely harbor gape- 
worms and hence in such localities are seldom likeh^ to spread 
infection. 

In those instances in which gapeworms develop in adult chickens 
or chickens approaching maturity the parasites are likely to live only 
a short time. 



THE TURKEY IMPOETAXT IX THE SPREAD OF GAPEWORMS. 13 

Ground contaminated by gapeworms is likeh' to -remain infective 
for at least a year after further infection of the soil has ceased. 

Losses from gapes can be greatly reduced if not altogether avoided 
by keeping young chickens on ground that has not been exposed to 
contamination within at least a year and that is protected from further 
contamination b}' excluding turkeys from it during its occupancy by 
the chickens. As gapeworms appear rarely to occur in adult chickens, 
brood hens may be associated with the 3'oung chickens with probably 
little risk of infection to the latter from that source. 

The simplest means of preA'enting or reducing losses from gapes 
appears to be the exclusion of turkej's from farms where chickens 
are raised. 

LIST OF REFERENCES. 

IIOKNE. 

1910. — Fra veterinaerlaboratoriets daglige imders0kelser. En kyllingsyg- 
dom. {Sytu/amus trachcalis) <Norsk Yet.-Tidsskr., Kristiania, 
V. 22 (6), Juiii, PI'- 15!)-1(>1, figs. 1-2. 
MoxTAGL". Geokgi:. 

1811. — Account of a species of Fasciola which infests tlie tracliea of poul- 
try, with a mode of cure. [Read Aug. 1, 1808] <Men]'. Werner 
Xat. Hist. Soc, Edinb. (1808-10), v. 1, pp. 194-198, pi. 7, fig. 4. 
VON Pocci, Fraxz Graf. 

1904. — Der Fasan nnd sein gefiihrlichster Feind. der Rotwurm <Verhandl. 
d. ornith, Gesellsch. in Bayern, ^Miinchen (1903), v. 4, n. F., v. 1, 
pp. 102-118, figs. 1-3. 1 pi., figs. 1-5. 
Ransom, Brayton H. 

1916. — Miscellaneous investigations of animal parasites <Rep. Clvef Bu- 
reaxx Animal Indust., U. S. Dept. Agric, Wash., p. 64. 

1917.— Idem <Ann. Rep. Dept. Agric, Wash. (1916), p. 130. 

1917. — ^Miscellaneous investigations of animal parasites <Rep. Chief 
Bureau Animal Indust., U. S. Dept. Agric, Wash., pp. 56-58. 

1918.— Idem <Ann. Rep. Dept. Agric, Washington (1917), pp. 122-124. 

1918. — Miscellaneous investigations of animal parasites <Rep. Chief Bu- 
reau Animal Indust., U. S. Dept. Agric, Wash., pp. 55-56. 

1919.— Idem <Ann. Rep. I>ept. Agric, AVash. (1918), pp. 12.5-126. 

1920. — On the life-history of the gape-worm (Syngamus trachealis). {In 
Proc Am. Soc. Zool., 17. Ann. Meet., St. Louis, Mo., Dec. 29-31, 
1919.) [Author's abstract] <Anat. Rec, Phila., v. 17 (5), Jan. 
20, pp. 330-331. 

1920. — Gapeworm in turkeys and chickens. [Note read before 38. Meet. 
Helminthol. Soc Wash., Oct. 18, 1919] <J. Parasitol., Urbana, 
111., V. 6 (4), June, pp. 200-201. [Issued Aug. 14.] 
Waite, Roy H. 

1920. — Earthworms — the important factor in the transmission of gapes in 
chickens <Bull. 234, Maryland Agric. Exper. Station, College 
Park, Jan., pp. 103-118, figs. 1-6. 

WiESENTHAL, ANDREW. 

1799.— [Gapes in poultry.] [Letter to editor, dated May 21, 1797] <Me(J. 
& Phys. J., Lond., v. 2 (8), Oct., pp. 204-205, 2 figs. 

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